The TZ18GN is a small notebook, weighing in at 1.15kg with an 11.1-inch display. It has a 32GB flash memory-based storage area and is driven by a low-energy 1.2GHz Core 2 Duo processor with 1GB of main memory. Its battery life is about 5 percent better than its cheaper hard-drive based sibling.

Sony says that the benefits of its flash memory over its hard drive-based cousin, the TZ17GN, include a faster boot time, lower weight, longer battery life and extended durability through having no hard drive which could fail.

However, the extended battery life is 11.5 hours, only thirty minutes more than the TZ17GN with its 100GB hard drive. This weighs approximately the same (1.2kg), uses the same keyboard and case, and has an eleven-hour battery life. It also costs about $3,600, $700 less than the TZ18GN, which is priced at $4,299 (£2,150 at ordinary conversion rates).

The battery life is the longest that can be expected. The actual life can be very much less. If you play a couple of DVDs on a long flight you'll probably exhaust it.

This flash Sony notebook has been given a low-power CPU to extend battery life, but the extension doesn't amount to much. The limited 32GB of storage says that owners with average data storage needs will quickly buy an external disk, thus nullifying its low weight.

AlienWare is offering a 64GB flash storage capacity notebook. You can specify a single 32GB solid state disk (SSD) unit with a 200GB hard drive, thus getting the flash speed boost and a respectable amount of storage capacity. It won't be as light as the Sony unit though.